United States Nuclear Regulatory Commission - Protecting People and the Environment

Bulletin 78-08: Radiation Levels from Fuel Element Transfer Tubes

                                UNITED STATES
                       NUCLEAR REGULATORY COMMISSION 
                    OFFICE OF INSPECTION AND ENFORCEMENT
                           WASHINGTON, D.C. 20555 
                                     
                               June 12, 1978 

                                                         IE Bulletin 78-08 

RADIATION LEVELS FROM FUEL ELEMENT TRANSFER TUBES 

Description of Circumstances: 

On April 5, 1978, two radiation protection technicians at Portland General 
Electric Company's Trojan Nuclear Power Plant received whole body radiation 
doses of 27.3 and 17.1 rem while performing a survey adjacent to an exposed 
section of the fuel element transfer tube during the plant's first refueling
outage. The exposures occurred in a shielded space inside the containment 
building which housed one of two fuel element transfer tube seismic relief 
bellows. The second bellows outside of containment had been provided with 
removable shielding and appropriate access controls. The bellows space 
inside containment was constructed with labyrinth-type shielding, however, 
access to the space was not controlled. The technicians were performing 
surveys in an attempt to identify a reported possible source of higher than 
expected radiation and had scheduled the survey to coincide with the passage 
of a fuel element through tile fuel element transfer tube. The technicians 
believed that the fuel element transfer tube was buried in the concrete 
beyond the compartment they occupied and assumed that the structure passing 
through the compartment was a ventilation duct. 

The licensee staff had performed surveys of all areas of the plant during 
the outage in an attempt to identify intermittent sources of radiation 
resulting from refueling activities; however, nothing significant was 
identified because of the transient nature of the resulting radiation 
fields. Subsequent to the exposures, the licensee performed surveys in 
numerous areas surrounding the general area of the fuel transfer tube with 
an irradiated fuel element stopped in the transfer tube. The surveys 
identified a number of areas previously unidentified where significant 
radiation streaming was present. The principal paths of radiation streaming 
were the narrow seismic relief spaces between the containment and internal 
and external structures. 



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IE Bulletin 78-08                                            June 12, 1978 

Action To Be Taken By Licensees: 

While the exposures above occurred at a pressurized water reactor, similar 
situations could occur at any reactor facility designed to transfer spent 
fuel between the reactor refueling canal and a spent fuel storage pool 
outside of containment by means of a fuel element transfer tube. 
Accordingly, holders of power, test and research reactor operating licenses 
where plant design incorporates a fuel element transfer tube, are to take 
the following actions: 

1.   Perform a thorough review of shielding design of plant areas adjacent 
     to the fuel transfer tube to identify potential high radiation areas, 
     both continuous and transient, as defined in 10 CFR 20.202(b). 

2.   Assure that positive control of access exists or is included in the 
     facility design for entryways into potential high radiation areas where
     a portion of a fuel transfer tube is accessible in an unshielded 
     condition. 

3.   Assure that points of access to potential high radiation areas 
     associated with accessible unshielded portions of a fuel transfer tube 
     are conspicuously posted in accordance with 10 CFR 20.203(c). 

4.   If the Action from Paragraph 1 above identifies the potential for 
     radiation streaming from shielded spaces, plan and conduct special 
     radiation surveys during the next refueling to identify and control 
     such areas. It is not necessary to survey in areas where the transfer 
     tube is exposed, but if it is found desirable, extreme care should be 
     exercised to control and limit personnel exposure. Care should also be 
     taken in planning surveys and fuel movements such that survey 
     requirements do not override any technical limitations on fuel 
     movement. 

5.   Confirm by written reply to the NRC Regional Office within 60 days that
     the actions for Items 1-4 above have been or are being taken. A record,
     detailing findings, actions taken, and actions to be taken, should be 
     retained for review by NRC during subsequent radiological safety 
     inspection. 

Approved by GAO, B180225 (R0072); clearance expires 7-31-80. Approval was 
given under a blanket clearance specifically for identified generic 
problems. 



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